On pages x-xi of his introduction to L. Feuerbach (1905 ed.) Plekhanov says:
“One German writer has remarked that for empirio-criticism experience is only an object of investigation, and not a means of knowledge. If that is so, then the distinction between empirio-criticism and materialism loses all meaning, and discussion of the question whether or not empirio-criticism is destined to replace materialism is absolutely shallow and idle.”
This is one complete muddle.
Fr. Carstanjen, one of the most “orthodox” followers of Avenarius, says in his article on empirio-criticism (a reply to Wundt), that “for The Critique of Pure Experience experience is not a means of knowledge but only an object of investigation." It follows that according to Plekhanov any distinction between the views of Fr. Carstanjen and materialism is meaningless!
Fr. Carstanjen is almost literally quoting Avenarius, who in his Notes emphatically contrasts his conception of experience as that which is given us, that which we find (das Vorgefundene), with the conception of experience as a “means of knowledge” in “the sense of the prevailing theories of knowledge, which essentially are fully metaphysical” (op. cit., p. 401). Petzoldt, following Avenarius, says the same thing in his Introduction to the Philosophy of Pure Experience (Bd. I, S. 170). Thus, according to Plekhanov, the distinction between the views of Carstanjen, Avenarius, Petzoldt and materialism is meaningless! Either Plekhanov has not read Carstanjen and Co. as thoroughly as he should, or he has taken his reference to “a German writer” at fifth hand.
What then does this statement, uttered by some of the most prominent empirio-criticists and not understood by Plekhanov, mean? Carstanjen wishes to say that Avenarius in his The Critique of Pure Experience takes experience, i.e.., all “human predications,” as the object of investigation. Avenarius does not investigate here, says Carstanjen (op. cit., p. 50), whether these predications are real, or whether they relate, for example, to ghosts; he merely arranges, systematises, formally classifies all possible human predications, both idealist and materialist (p. 53), without going into the essence of the question. Carstanjen is absolutely right when he characterises this point of view as “scepticism par excellence” (p. 213). In this article, by the way, Carstanjen defends his beloved master from the ignominious (for a German professor) charge of materialism levelled against him by Wundt. Why are we materialists, pray?—such is the burden of Carstanjen’s objections—when we speak of “experience” we do not mean it in the ordinary current sense, which leads or might lead to materialism, but in the sense that we investigate everything that men “predicate” as experience. Carstanjen and Avenarius regard the view that experience is a means of knowledge as materialistic (that, perhaps, is the most common opinion, but nevertheless, untrue, as we have seen in the case of Fichte). Avenarius entrenches himself against the “prevailing” “metaphysics” which persists in regarding the brain as the organ of thought and which ignores the theories of introjection and co-ordination. By the given or the found (das Vorgefundene), Avenarius means the indissoluble connection between the self and the environment, which leads to a confused idealist interpretation of “experience.”
Hence, both the materialist and the idealist, as well as the Humean and the Kantian lines in philosophy may unquestionably be concealed beneath the word “experience"; but neither the definition of experience as an object of investigation,nor its definition as a means of knowledge is decisive in this respect. Carstanjen’s remarks against Wundt especially have no relation whatever to the question of the distinction between empirio-criticism and materialism.
As a curiosity let us note that on this point Bogdanov and Valentinov, in their reply to Plekhanov, revealed no greater knowledge of the subject. Bogdanov declared: “It is not quite clear” (Bk. III, p. xi).—"It is the task of empirio-criticists to examine this formulation and to accept or reject the condition.” A very convenient position: I, forsooth, am not a Machian and am not therefore obliged to find out in what sense a certain Avenarius or Carstanjen speaks of experience! Bogdanov wants to make use of Machism (and of the Machian confusion regarding “experience"), but he does not want to be held responsible for it.
The “pure” empirio-criticist Valentinov transcribed Plekhanov’s remark and publicly danced the cancan; he sneered at Plekhanov for not naming the author and for not explaining what the matter was all about (op. cit., pp. 108-09). But at the same time this empirio-critical philosopher in his answer said not a single word on the substance of the matter, although acknowledging that he had read Plekhanov’s remark “three times or more” (and had apparently not under stood it). Oh, those Machians!
 Vierteljabrsschrift für wissenschaftliche Philosophie, Jahrg. 22, 1898, S. 45. —Lenin
 THIS FOOTNOTE has been moved into BODY OF DOCUMENT.